Optical Biosensing Applications Research Articles

Real‐Time Nanoscale Bacterial Detection Utilizing a 1DZnO Optical Nanobiosensor

One‐dimensional zinc oxide nanomaterials (1DZnO) have emerged as promising, cost‐effective nanoplatforms with adjustable properties suitable for electrochemical and optical biosensing applications. In this work, modifications in the inherent photoluminescent response of 1DZnO are harnessed to develop a novel immunosensor tailored for detecting enteropathogenic Escherichia coli. This nanobiosensor demonstrates a modulation in photoluminescence signal, effectively responsive to analyte concentrations ranging from 1 × 102 to 1 × 108 CFU mL−1, with direct visualization of targeted bacterial cells over 1DZnO structures through scanning electron microscopy. The conceptualization of this nanobiosensor is focused on a real‐time contact strategy that can significantly reduce processing and response times for pathogen detection, prospected for emergency scenarios. With this aim, the detection process unfolds in real time, with a mere 5–10 s interaction time, corroborated by the standard polymerase chain reaction approach. This synergistic validation underscores the reliability and precision of the developed biosensor. Notably, the utility of 1DZnO nanoplatforms extends beyond the realm of enteropathogenic E. coli, as the biosensing performance exhibited here holds promise for analogous applications involving other medically pertinent pathogens. This study paves the way for the broader implementation of 1DZnO‐based biosensors in medical diagnostics, offering rapid, sensitive, and real‐time detection capabilities.

Novel synthesis of 1-D silicon nanowires grown on pyramidal black silicon substrates and intense visible emission

This work shows a new way to grow 1-D Silicon Nanowires (SiNWs) over pyramidal black silicon used as substrates. These nanostructures are grown by the plasma-assisted vapor–liquid-solid (VLS) as a bottom-up process, using tin thin films as a catalytic metal and dichlorosilane gas as a silicon precursor. SiNWs were obtained with diameters from 300-600 nm and 4–6 µm lengths on the black silicon surface. Due to the pyramid-shaped and porous nature of the black silicon surface, SiNWs form a complex mesh nanostructure. This network has a large surface area and exhibits intense and effective photoluminescence with a peak in the green spectrum, which is attributed to the quantum confinement effect that occurred in small nc-Si embedded inside SiNWs. These structural configurations hold significant promise for applications in optical biosensors, solar cells, and other prospective fields.

Analysis of Fluid Replacement in Two Fluidic Chambers for Oblique-Incidence Reflectivity Difference (OI-RD) Biosensor.

Optical biosensors have a significant impact on various aspects of our lives. In many applications of optical biosensors, fluidic chambers play a crucial role in facilitating controlled fluid delivery. It is essential to achieve complete liquid replacement in order to obtain accurate and reliable results. However, the configurations of fluidic chambers vary across different optical biosensors, resulting in diverse fluidic volumes and flow rates, and there are no standardized guidelines for liquid replacement. In this paper, we utilize COMSOL Multiphysics, a finite element analysis software, to investigate the optimal fluid volume required for two types of fluidic chambers in the context of the oblique-incidence reflectivity difference (OI-RD) biosensor. We found that the depth of the fluidic chamber is the most crucial factor influencing the required liquid volume, with the volume being a quadratic function of the depth. Additionally, the required fluid volume is also influenced by the positions on the substrate surface bearing samples, while the flow rate has no impact on the fluid volume.

Advances in biosensors for poison detection applications

This paper discusses the applications and challenges of biosensors in drug and toxin detection, highlighting the practical value of biosensors and their role in forensic investigations, medical research, and environmental monitoring. Because drug abuse poses a major threat to human health and society, there is an urgent need for technologies that can quickly, portable, and sensitively detect drugs in common biological samples. This paper introduces the detection of animal and plant toxins, including snake venom, spider toxins, cyanide in plants, etc., and discusses the importance of detection of these toxins in medical and forensic fields. The development of biosensor technology, including the application of optical biosensors and electrochemical biosensors based on enzyme inhibition, is also summarized, and the role of these sensors in drug research and environmental monitoring is introduced. In addition, the paper highlights the potential of nanotechnology to improve the sensitivity and specificity of biosensors, as well as the future applications of biosensors in health, environmental monitoring, and agriculture. Finally, the paper points out the limitations of current biosensor research, and puts forward the direction of future research, emphasizing the need to develop simpler, more sensitive and more specific biosensors to broaden their practical applications.

High-Q Fano resonances in all-dielectric metastructures for enhanced optical biosensing applications.

Fano resonance with high Q-factor is considered to play an important role in the field of refractive index sensing. In this paper, we theoretically and experimentally investigate a refractive index sensor with high performance, realizing a new approach to excite multiple Fano resonances of high Q-factor by introducing an asymmetric parameter to generate a quasi-bound state in the continuum (BIC). Combined with the electromagnetic properties, the formation mechanism of Fano resonances in multiple different excitation modes is analyzed and the resonant modes of the three resonant peaks are analyzed as toroidal dipole (TD), magnetic quadrupole (MQ), and magnetic dipole (MD), respectively. The simulation results show that the proposed metastructure has excellent sensing properties with a Q-factor of 3668, sensitivity of 350 nm/RIU, and figure of merit (FOM) of 1000. Furthermore, the metastructure has been fabricated and investigated experimentally, and the result shows that its maximum Q-factor, sensitivity and FOM can reach 634, 233 nm/RIU and 115, respectively. The proposed metastructure is believed to further contribute to the development of biosensors, nonlinear optics, and lasers.

Optical biosensing systems for a biological living body

AbstractWith the development of technology, biosensors are increasingly used in the biomedical field. Due to the high sensitivity of optical signals, good stability, high signal‐to‐noise ratio, and different spectral characteristics of different analytes, optical biosensors can achieve direct and real‐time detection of analytes with high specificity compared with traditional analytical techniques. In view of the rapid development of optical biosensors for in vivo applications and their promising future, we have attempted to summarize the working principles and recent advances in application in humans, with the aim of helping readers to gain an in‐depth and detailed understanding of optical biosensors developed in recent years for applications in the biological living body. In this review, we focus on some of the current widely used and promising optical biosensors, including colorimetric biosensors, fluorescence biosensors, and surface‐enhanced‐Raman‐scattering‐based biosensors. The working principles for each type of optical biosensor are concisely described and the application of the biosensor in the living body is summarized by category. We conclude by looking at the prospects of in vivo applications of optical biosensors.

Microfluidic Platforms for Single Cell Analysis: Applications in Cellular Manipulation and Optical Biosensing

Cellular heterogeneity of any tissue or organ makes it challenging to identify and study the impact and the treatment of any disease. In this context, analysis of cells at an individual level becomes highly relevant for throwing light on the heterogeneous nature of cells. Single cell analysis can be used to gain insights into an overall view of any disease, thereby holding great applications in health diagnosis, disease identification, drug screening, and targeted delivery. Various conventional methods, such as flow cytometry, are used to isolate and study single cells. Still, these methods are narrower in scope due to certain limitations, including the associated processing/run times, the economy of reagents, and sample preparation. Microfluidics, an emerging technology, overcomes such limitations and is now being widely applied to develop tools for the isolation, analysis, and parallel manipulation of single cells. This review systematically compiles various microfluidic tools and techniques involved in single cell investigation. The review begins by highlighting the applications of microfluidics in single cell sorting and manipulation, followed by emphasizing microfluidic platforms for single cell analysis, with a specific focus on optical sensing-based detection in a high-throughput fashion, and ends with applications in cancer cell studies.

Enhancement of elastic properties and surface plasmon resonance with the addition of boron oxide to the ZnO−SiO2 glass system

Glass substrates, with their ultrasonic and enhanced Raman signals, are ever-demanding for medical applications. This paper reports the effect of boron addition to the enhancement of the elastic properties and Raman shifting in the Surface Plasmon Resonance results for the zinc borosilicate glass substrate that can be used for optical biosensor applications. Such glasses were prepared by melt–the quenching method and characterized using a densimeter, X-ray diffraction measurement, Fourier transforms infrared spectroscopy, ultrasonic, and surface plasmon resonance spectroscopy. Results from the current study demonstrated how the composition of the glass influences the physical and elastic moduli of the boron-doped zinc silicate series. The physical characteristics of the zinc silicate glasses were predicted to alter significantly after adding boron as a modifier. The glass density decreased from 3392 to 2983 kg/m3 as the percentage of boron increased from 0.10 to 0.20 wt.%, then increased to 3191 kg/m3 at 0.30 wt.%. The X-ray diffraction and Fourier transforms infrared spectroscopy techniques verified the amorphous glass phase. The ultrasonic method determined the glass's ultrasonic longitudinal and shear velocity at a 5 MHz resounding recurrence at room temperature to study elastic moduli. When boron content is added, the longitudinal, Young, shear, and bulk moduli exhibit a decreasing and increasing trend. As the boron content increases and behaves as a modifier, the number of non-bridging oxygen will increase, which will cause the glass network to expand. In addition, the increase in Eopt occurs from 3.4883 to 3.4331 because the sample has a higher number of non-bridging oxygen. The shift for Otto configuration of the SPR results occurs with the increase of boron concentration. The fabricated glass can potentially be used to construct an integrated silicon-based glass substrate for an optical sensor.

Comprehensive Review on Synthesis, Applications, and Challenges of Graphene Quantum Dots (GQDs)

Carbon-based nanomaterials are contemporary and are outpacing the technology platform. Graphene quantum dots (GQDs) had a significant impact on the subject of bioengineering, pharmaceuticals, biomedicine, biosensors, fuel, energy, etc. Depending on how quickly this field is developing, it is important to recognize the new difficulties that GQDs have to overcome. This is incredibly significant because many novel applications and innovations that have made GQD synthesis easier recently have not been systematically evaluated in prior studies. Their ability to combine the benefits of quantum dots, sp2 carbon materials (large specific surface area), and have rich functional groups at the edge makes them special. The naturally occurring inert carbon helps to stabilize chemical and physical characteristics and makes significant advancements in the creation of benchmark photocatalysts. Moreover, current challenges and potential of these rapidly developing GQDs are emphasized. The future of GQD research is limitless, according to the assessment in this review, notably if future research focuses on simplicity of purification and ecofriendly synthesis. This feature article offers a realistic summary on recent developments in the synthesis, characteristics, and uses of GQDs. Frequent review articles focusing on the progress of GQDs for specific applications are published but a thorough review article on GQDs for their numerous uses has not yet been published. The recent trends of scientific research based on new optical biosensing applications, including the comprehensive applications of different zero-dimensional nanomaterials, specially GQDs are discussed in this study.

Optically Active Nanomaterials and Its Biosensing Applications—A Review

This article discusses optically active nanomaterials and their optical biosensing applications. In addition to enhancing their sensitivity, these nanomaterials also increase their biocompatibility. For this reason, nanomaterials, particularly those based on their chemical compositions, such as carbon-based nanomaterials, inorganic-based nanomaterials, organic-based nanomaterials, and composite-based nanomaterials for biosensing applications are investigated thoroughly. These nanomaterials are used extensively in the field of fiber optic biosensing to improve response time, detection limit, and nature of specificity. Consequently, this article describes contemporary and application-based research that will be of great use to researchers in the nanomaterial-based optical sensing field. The difficulties encountered during the synthesis, characterization, and application of nanomaterials are also enumerated, and their future prospects are outlined for the reader's benefit.

A Framework for Biosensors Assisted by Multiphoton Effects and Machine Learning.

The ability to interpret information through automatic sensors is one of the most important pillars of modern technology. In particular, the potential of biosensors has been used to evaluate biological information of living organisms, and to detect danger or predict urgent situations in a battlefield, as in the invasion of SARS-CoV-2 in this era. This work is devoted to describing a panoramic overview of optical biosensors that can be improved by the assistance of nonlinear optics and machine learning methods. Optical biosensors have demonstrated their effectiveness in detecting a diverse range of viruses. Specifically, the SARS-CoV-2 virus has generated disturbance all over the world, and biosensors have emerged as a key for providing an analysis based on physical and chemical phenomena. In this perspective, we highlight how multiphoton interactions can be responsible for an enhancement in sensibility exhibited by biosensors. The nonlinear optical effects open up a series of options to expand the applications of optical biosensors. Nonlinearities together with computer tools are suitable for the identification of complex low-dimensional agents. Machine learning methods can approximate functions to reveal patterns in the detection of dynamic objects in the human body and determine viruses, harmful entities, or strange kinetics in cells.

Surface plasmon resonance sensor for chemical and bio-sensing application: A review

Surface Plasmon Resonance (SPR) sensor are label-free optical fiber sensor used for advanced optical biosensing applications. They also made considerable strides in the sensing of different chemical and biological organisms. The theory and implementation of SPR sensors are introduced and thoroughly summarized in this study. We describe the mechanism of SPR sensors and provide a detailed overview of the optical architecture, including the substrate and surface plasmon excitation modes. Furthermore, applications based on SPR sensors are represent-ed in chemical and biosensing application.

Near‐Infrared Optical Sensing of Biomacromolecules with Upconversion Nanoplatforms

Optical sensing and imaging have perceived massive success in biomedical analysis and disease diagnosis in terms of minimal invasiveness, good sensitivity, high accuracy, and time‐/cost‐effectiveness. Upconversion nanoparticles (UCNPs) as a kind of promising luminescent material hold many merits like unique frequency‐converting capability, emission fine‐tuning, low auto‐fluorescence interference, good tissue‐penetration ability, high photostability, and excellent biocompatibility, which are widely applied for optical sensing of diverse chemically or biologically derived analytes. Extensive efforts are dedicated to the rational fabrication of reliable upconversion nanoplatforms (UCNs) through ingenious modulation of the luminescent energy transfer process for various optical biosensing applications. Herein, the advancement of biomacromolecules (e.g., nucleic acids, proteins, and enzymes) detection using multiplex UCNs from on‐paper platforms to in‐solution as well in living systems is specifically focussed. Detailed summarizations of the probe design strategy, responsive mechanisms, and sensing performance have been presented. In addition, based on the current research achievements, the challenges and future perspectives are emphasized to facilitate further clinical sensing utilizations with upconversion photonic technology.

Enhanced Optical Biosensing by Aerotaxy Ga(As)P Nanowire Platforms Suitable for Scalable Production.

Sensitive detection of low-abundance biomolecules is central for diagnostic applications. Semiconductor nanowires can be designed to enhance the fluorescence signal from surface-bound molecules, prospectively improving the limit of optical detection. However, to achieve the desired control of physical dimensions and material properties, one currently uses relatively expensive substrates and slow epitaxy techniques. An alternative approach is aerotaxy, a high-throughput and substrate-free production technique for high-quality semiconductor nanowires. Here, we compare the optical sensing performance of custom-grown aerotaxy-produced Ga(As)P nanowires vertically aligned on a polymer substrate to GaP nanowires batch-produced by epitaxy on GaP substrates. We find that signal enhancement by individual aerotaxy nanowires is comparable to that from epitaxy nanowires and present evidence of single-molecule detection. Platforms based on both types of nanowires show substantially higher normalized-to-blank signal intensity than planar glass surfaces, with the epitaxy platforms performing somewhat better, owing to a higher density of nanowires. With further optimization, aerotaxy nanowires thus offer a pathway to scalable, low-cost production of highly sensitive nanowire-based platforms for optical biosensing applications.

Better colloidal lithography: Tilt-rotate evaporation overcomes the limits of plasma etching

Colloidal lithography (CL) is a promising method for large-area fabrication of nanohole and nanodot arrays with applications in optical biosensing, separations, and magnetic data storage. However, reducing the diameter of the polystyrene sphere mask by plasma etching unavoidably increases their coefficient of variation (CV) and deforms their shape, thereby limiting the pitch-to-hole-diameter ratio of the resulting nanohole array to less than 3:1 and the minimum hole size to 200 nm with a 10% or better CV. We show that tilt-rotate evaporation colloidal lithography (TRE-CL) breaks the trade-off between hole diameter and polydispersity by leveraging glancing angle evaporation, not plasma etching, to adjust the hole size. TRE-CL allows pitch-to-hole-diameter ratios as high as 7:1 and nanohole diameters down to 60 nm while maintaining a nearly constant CV below 10% and hole circularity above 91%. We transfer these hole arrays into ultrathin Si3N4 films to form nearly-monodisperse microsieves for separation applications. Furthermore, we extend TRE-CL to fabricate adhesion-layer-free plasmonic Au nanodot arrays down to 70 nm in diameter with 10% CV.

Fourier spotting: a novel setup for single-color reflectometry

Single-color reflectrometry is a sensitive and robust detection method in optical biosensor applications, for example for bioanalysis. It is based on the interference of reflected monochromatic radiation and is label free. We present a novel setup for single-color reflectometry based on the patented technology of Berner et al. from 2016. Tilting areas of micro-mirrors allow us to encode the optical reflection signal of an analyte and reference channel into a particular carrier frequency with the amplitude being proportional to the local reflection. Therefore, a single photodiode is sufficient to collect the signals from both channels simultaneously. A 180∘ phase shift in the tilt frequency of two calibrated micro-mirror areas leads to a superposition of the analyte and reference signal which enables an efficient reduction of the baseline offset and potential baseline offset drift. A performance test reveals that we are able to detect changes of the refractive index n down to Δn < 0.01 of saline solutions as regents. A further test validates the detection of heterogeneous binding interaction. This test compromises immobilized testosterone-bovine serum albumin on a three-dimensional layer of biopolymer as ligand and monoclonal anti-testosterone antibodies as analyte. Antibody/antigen binding induces a local growth of the biolayer and change in the refractive index, which is measured via the local change of the reflection. Reproducible measurements enable for the analysis of the binding kinetics by determining the affinity constant KA = 1.59 × 10− 7 M− 1. In summary, this work shows that the concept of differential Fourier spotting as novel setup for single-color reflectometry is suitable for reliable bioanalysis.Graphical

Recent progress in 0D optical nanoprobes for applications in the sensing of (bio)analytes with the prospect of global health monitoring and detailed mechanistic insights

In the present review, the current trends of the research endeavours (2017–2022) based on emerging optical biosensing applications by various 0D nanomaterials have been comprehensively described towards the detection of targeted bio-analytes.

Functionalization of Oxide‐Free Silicon Surfaces for Biosensing Applications

AbstractAs an alternative to standard silicon biofunctionalization protocol based on alkoxysilanes that bind to SiO2 on oxidized silicon substrates, several protocols to form bifunctional interlayers that directly bind to the silicon surface via a strong SiC bond have been developed during the last decades. These interlayers are more stable, and the lack of an insulating layer between the substrate and the interlayer reduces electric noise in biosensor devices. SiC monolayers are not yet regularly applied as the protocols are more complex and generally require an inert gas atmosphere. However, a variety of applications and new methods to form bifunctional SiC interlayers are recently developed. Here, the role these innovative protocols and interlayers play in biofunctionalization of silicon surfaces is reviewed and their applications in electrochemical, microelectromechanical, and optical biosensing are reported. From the analysis of the current situation, it can be concluded that the advantageous properties offered with this approach in many cases more than outweigh the additional processes to form SiC bonded interlayers and the approach is predicted to expand the applications of future silicon‐based biosensors.

Polymer-Surfactant Driven Interactions and the Resultant Microstructure in Protein-Containing Liquid Crystal Droplets.

Integration of molecular liquid crystals (LCs) with functional proteins can provide new class of materials for potential applications in optical biosensing. However, hydrophobic nematic LCs (length ∼ 1-2 nm) and hydrophilic proteins, size ∼ O (nm), do not intermix without chemical modification of at least one of them. Bioconjugation of proteins with a polyethylene glycol-based polymeric surfactant (PS) can provide a core-shell system that is sequestered within nonaqueous LC (4-cyano-4'-pentylbiphenyl) microdroplets. However, the nature of interactions between the components and detailed understanding of the resultant hybrid microstructure remains unclear. Here, using a combination of isothermal titration calorimetry (ITC), fluorescence microscopy, and infrared-imaging spectroscopy, we show that strong hydrophobic interactions between the LC and PS drives the sequestration of a myoglobin-PS (Mb-PS; dispersed in the aqueous phase) into the LC spherical microdroplets or even into a bulk LC phase. The average values of both, the binding constant and the standard molar enthalpy change, are increased by approximately a factor of 2.5 times when the unmodified Mb is conjugated to the PS. Small-angle X-ray scattering studies reveal that LC molecules act as a solvent for the Mb-PS conjugate; furthermore, the LC long-range order is disturbed due to mixing, as exemplified by the change in its coherence length from 8.9 to 5.7 nm. Detailed all-atomistic molecular dynamic simulations for a three-component PS-water-LC system show a change in interaction energy of -144 kJ mol-1 PS-1 upon the contact of PS chains (initially dispersed in water) with LC and agree with the ITC experiments.

Optical biosensing of lysozyme

Lysozyme, also called “muramidase”, is an antimicrobial enzyme with antibacterial activity with importance in medicine, food industry, protein studies and enzymology. Lysozyme is also a model analyte in the biosensing field. Optical biosensors have been proposed as alternative analytical tools to the standard detection of lysozyme by ELISA, chromatographic methods or capillary electrophoresis. These biosensors combine specific recognition via antibodies, aptamers, peptides, Micrococcus lysodeikticus bacteria and molecularly imprinted polymers (MIPs) with sensitive detection based on luminescence, surface plasmon resonance (SPR), surface enhanced Raman spectroscopy (SERS), colorimetry etc. To deliver shorter response time, a better sensitivity, but also a lower cost, many of the sensing schemes included nanomaterial and enzyme-enabled amplification. Several biological and food matrices were explored for the potential applications of optical biosensors. The review presents the bioreceptors used and provides illustrative details on the sensing schemes, discussed in relation to the method of detection. Challenges for real samples applications and perspectives of optical biosensors for lysozyme are also presented.